Understanding blood alcohol content levels

The basis for many DUI arrests, the amount of alcohol in people’s bodies is known as their BAC level, and may rise based on varying factors.

In 2013 alone, the most recent year with available statistics, there were 160,388 motorists arrested for driving under the influence across the state, according to the California Department of Motor Vehicles. Beyond their own observations and drivers' performance on roadside tests, the authorities often base such charges on people's blood alcohol content levels. Understanding BAC levels may help motorists protect themselves from unnecessary arrests.

What is blood alcohol content?

When people drink alcoholic beverages, the alcohol is absorbed through their small intestines and stomachs. It then enters the bloodstream and is carried throughout the body. The measurement of the amount of alcohol in a person's body is known as the blood alcohol content, or BAC, level. In California and other states, motorists may be arrested if their BAC levels reach 0.08 percent or more.

How is BAC measured?

Driver's BAC may be obtained using blood, urine or breath tests. Generally, this measurement is obtained by assessing the weight of alcohol in a particular volume of blood. Depending on a number of factors, BAC levels reach their peak within 30 to 70 minutes of consuming an alcoholic beverage.

What factors affect drivers' BAC?

The rate at which people's BACs rise may be affected by several factors. According to the National Highway Traffic Safety Administration, these include the following:

  • The number of drinks consumed
  • How fast the drinks were consumed
  • The driver's weight
  • The driver's gender
  • Whether the driver has had anything to eat

While taking certain medications or using certain drugs may enhance the effects of alcohol and impairment on motorists' bodies, they will not impact their BAC levels.

Many are of the belief that the type of alcohol they consume affects their BAC, with distilled liquor resulting in higher levels than beer, for example. This is not the case, however. Generally, the average 1.5 ounce of 80 proof alcohol, five-ounce glass of wine and standard 12-ounce beer contain the same amount of alcohol.

Obtaining legal representation

BAC evidence is certainly a key piece of evidence, but there are factors like time of consumption, test accuracy and other issues relating to your blood alcohol at time of driving. Your BAC does not remain constant, it is either rising or falling. If you just drank before the arrest, you may be higher testing later at the jail than at the time of driving as you are still "absorbing". Conversely if you stopped drinking a while before the stop, you may test lower at the station than you were at the time of driving, this is called "burn off" as the alcohol is metabolized. Contacting a DUI attorney after an arrest is important to evaluate your case, explain the process and understand other aspects of your case, including possible resolutions and defenses.